Unraveling the Whooping Cough Epidemic

California's Pertussis Epidemic the Worst in 55 Years; Outbreaks Now Occurring in Other States

Medically Reviewed by Laura J. Martin, MD on October 01, 2010
8 min read

In California, 2010 started out much like many others for the public health detectives who keep an eye on infectious diseases.

But by the end of the year, 10 California babies were dead from whooping cough, aka pertussis, a highly contagious disease that’s preventable by a vaccine.

Kathleen Harriman, PhD, MPH, RN, chief of the California Department of Public Health's vaccine preventable disease epidemiology section, says 9,477 confirmed, probable, and suspected cases of pertussis were reported to the state in 2010 -- the most in 65 years. Cases have surged in other states, too.

In eight of the California cases that resulted in deaths, the babies had been seen by their doctor or an emergency room doctor but were not initially diagnosed with whooping cough.

The stories were shockingly familiar to Mariah Bianchi of San Francisco.

In 2005, Bianchi lost her newborn son, Dylan, to pertussis. She had sought repeated medical attention for her own symptoms, fearful she would pass on whatever she had to her son, Cole, then 3, and to Dylan.

Once doctors began to suspect pertussis, little Dylan went downhill quickly. He died within 48 hours after doctors started treatment and hospitalized him. He was just over 2 weeks old. Cole recovered.

For Bianchi, the nine deaths were a turning point that increased her commitment to activism. She had joined the immunization coalition in San Francisco in 2009, but now also volunteers for the state coalition. She often shares her experience as she encourages parents to get and keep their children vaccinated, to get a booster shot themselves, and to make doctors aware of the symptoms of whooping cough.

"It breaks my heart that these nine babies' parents are going to have to live with that grief," says Bianchi, a critical care nurse. "It almost takes things like this to make people more aware.”

Pertussis can cause serious illness at any age, with early symptoms such as a runny nose and mild cough lasting up to two weeks, and the coughing fits sometimes persisting for 10 weeks or longer. The infection is typically less severe in teens and adults than in babies.

Once the symptoms of the bacterial respiratory infection set in -- including the strong cough that leaves patients making a ''whooping'' sound as they try to catch their breath -- young infants in particular can deteriorate quickly, developing a high white blood cell count, respiratory distress, and deadly pneumonia.

All the California infants who died were under 3 months old and thus not fully protected against pertussis. The five-dose series of pertussis vaccine to protect against whooping cough typically begins at age 2 months, but sufficient protection isn't achieved until about the third dose, at around 6 months, experts say.

To help protect infants, it is particularly important they stay away from someone who is not immunized, whether it is a child who never received the vaccine or an adult who has waning immunity because they did not get a booster shot.

In California, which allows parents to exempt their children from vaccinations for philosophical reasons, the rate of unvaccinated children in 2009 was 2%, CDC figures show. Some parents, fearing side effects from vaccines, depend instead on the concept of ''herd immunity.” Because many others are vaccinated, their own child's chances of catching the disease theoretically are lower.

''Those who don't vaccinate contribute'' to the epidemic, but the cyclical nature of the disease is mainly to blame, says James Cherry, MD, a professor of pediatrics at the David Geffen School of Medicine at the University of California Los Angeles, who has studied pertussis for 30 years. He reviewed the fatal California cases for the state.

Public health officials agree that unvaccinated children are just one factor that has played a role in the epidemic. Others include:

  • The cyclical nature of pertussis. Pertussis typically reappears every three to five years. “The main thing is the cycle,” Cherry says. The last cyclical peak in California, Harriman says, was in 2005. Fueling the fire, the disease is also highly contagious, Harriman says.
  • Unprotected adults. ''Immunity to pertussis wanes with increasing time since vaccination, so adolescents and adults need to boost their immunity," says Thomas Clark, MD, MPH, medical officer and epidemiology team leader of the CDC's National Center for Immunization and Respiratory Diseases.
  • Difficulty in diagnosing. Because the first symptoms may be mild, whooping cough is not always easy to diagnose, says Brian Johnston, MD, director of the emergency department at White Memorial Medical Center in Los Angeles, where some children have been hospitalized with pertussis, a rare occurrence there. The organism, Bordetella pertussis, can be ''hard to culture," he says. "It is extremely difficult, the diagnosis. You have to be clinically suspecting it all the time," and be prepared to prescribe antibiotics -- the treatment for whooping cough -- even though doctors have been schooled in general not to over-prescribe them.
  • Mutations in the bacteria. Pertussis bacteria may be mutating and outwitting the vaccine, according to a Dutch researcher who published his findings in 2009 in the journal Emerging Infectious Diseases.

Not to blame, Harriman says, are immigrants. Nine of the 10 California fatalities were Hispanic infants. That could be linked to the size of Hispanic households, typically larger than those of other ethnic groups, she says. More household contacts increase the chances of someone there being exposed to whooping cough.

"Pertussis has never left the U.S., ever,” Harriman says. “We don't need anyone to bring it here, it's here."

As the epidemic spreads, no one can say for sure if it's peaked or just beginning to gain steam. Several other states have reported a surge in cases, according to CDC spokesman Jeff Dimond, including South Carolina, New York, Michigan, Ohio, and Minnesota.

Public health officials are urging parents to be sure their children's vaccinations are up to date and to get an adult booster themselves. Probably only 6% of U.S. adults have gotten that booster, according to CDC estimates.

Public health officials are also promoting a concept called ''cocooning": being sure anyone in contact with infants, particularly those too young to get the first vaccine dos, are immunized against pertussis.

Here are the CDC’s vaccine recommendations:

  • For young children,five doses of the vaccine called DTaP (diphtheria, tetanus, pertussis) given at 2, 4, 6, and 15-18 months, and 4-6 years.
  • For those 11 through 18, the CDC recommends one booster dose of Tdap.
  • Adults 19 through 64 should get a dose of Tdap.

Although the CDC does not have a recommendation on the use of pertussis in people over age 65, as a whooping cough booster is not licensed for this age group, it says people 65 and older can talk to their doctor to see if Tdap is a good decision for them. Doctors may choose to give the Tdap to people 65 and older, especially if they are caring for an infant.

The California Department of Public Health broadened its recommendation for booster doses of pertussis, suggesting it for anyone 7 or older who isn't fully immunized, including seniors, as well as women of childbearing age, before, during, or right after pregnancy.

CDC epidemiologist Thomas Clark says he hopes that the tragedy of the epidemic may help change the minds of people concerned about vaccines.

"I hope it makes [people] realize that diseases like pertussis haven't gone away,” says Clark, MD, MPH, the CDC's medical officer and epidemiology team leader. “I think some people thought whooping cough was a disease of the past."

The state of California has issued alerts to doctors, urging them to be vigilant for possible cases. In Los Angeles County, officials are pushing widespread vaccinations, says Jonathan Fielding, MD, director of public health for the county and county health officer. Like others, he advocates the cocooning concept. '''I think we have to be much more careful about who is around small babies," he tells WebMD.

"Hospitals and doctors should be keeping track of immunizations and making sure anyone who is going to be around small children is up to date on immunizations," he says.

Hospitals are doing just that. At Cedars-Sinai Medical Center in Los Angeles, for instance, women who have given birth there and have not had the vaccine are urged to get it before going home, says Debbie Lehman, MD, associate director of pediatric infectious diseases at Cedars-Sinai's Maxine Dunitz Children's Health Center.

The medical center also is urging all health care workers to be up to date on pertussis vaccine. If they refuse, they must sign a ''declination" form, she tells WebMD.

Lehman is hopeful that will persuade them to change their mind and get vaccinated. The declination form seems to work that way, she says, for the influenza vaccine. She is also reaching out to fathers and grandparents of newborns, urging them to visit their own doctors and get immunized.

If parents are concerned that their child has pertussis -- and the symptoms seem to support that concern, Cherry urges them to ask the doctor for testing. Of some doctors, he says, "They have to be prodded. The illness doesn't look bad."

Parents can also ask for a white blood cell count, as high counts are common in severely ill babies, says Cherry, who has worked as a consultant for the new adult vaccines and served on a speaker's bureau for vaccine makers.

While public health and safety fuel the efforts of the CDC and the states, Bianchi seems driven by grief turned to activism.

In an instant, she can take you back to that day in the hospital, when she and her husband, David, frantically followed the ambulance that transferred their son to another facility to better care for him, then heard the tragic news that their baby had gone into cardiac arrest. CPR had proven fruitless, and the parents were offered a last visit.

"He had the sweetest face," Mariah says. "A little heart-shaped chin, and auburn hair."

Just as quickly, she comes back to the moment and her decision to channel ''all that anger and all that energy'' to making sure other children won't be lost to a preventable disease. "I know what it's like to have this happen."